Solid solutions in sputter-deposits of iron with 0 to 5 Wt Pct C

Abstract

Supersaturated iron-carbon solid solutions containing 0.06, 0.18, 0.66, 2, 3, and 5 wt pct C were produced by sputter-deposition at 6° to 21°C. Homogeneous deposits of the same carbon composition as the multiphase source materials were produced by high rate (up to 0.0004 in. per hr) sputtering techniques and were 0.005 to 0.027 in. thick. The microhardnesses of the deposits were higher than the hardnesses of martensite with the same carbon content. The hardness increased rapidly from 680 Dph for 0.06 wt pct C content to an unusually high maximum of 1240 Dph at 2 wt pct C and then decreased slowly to 920 Dph at 5 wt pct C. The 0.06, 0.18, and 0.66 wt pct C deposits were bcc, and the 2 and 3 wt pct C deposits were bct. The tetragonality of the 5 wt pct C deposit was detected only after tempering at 150°C. Lattice parameterc/a ratios for the tetragonal deposits were lower than expected from extrapolated martensite data, and they corresponded to the equationc/a=1.06+0.019 (wt pct C). Nevertheless, thec/a ratio of 1.10 for 5 wt pct C deposit was higher than previously observed for martensite. No evidence of a martensitic transformation was found in the microstructures, which typically consisted of 0.5 to 1.0 μ diam columnar grains. Hardness data from tempered eposit samples and the lack of tetragonality of the low carbon deposits indicated that autotempering occurred during sputter-deposition.